Co- or Ni-modified Sn-MnOx low-dimensional multi-oxides for high-efficient NH-SCR De-NOx: Performance optimization and reaction mechanism.

NH-SCR performances were explored to the relationship between structure morphology and physio-chemical properties over low-dimensional ternary Mn-based catalysts prepared by one-step synthesis method. Due to its strong oxidation performance, Sn-MnOx was prone to side reactions between NO, NH and O, resulting in the generation of more NO and NO, here most of NO was driven from the non-selective oxidation of NH, while a small part generated from the side reaction between NH and NO. Co or Ni doping into Sn-MnOx as solid solution components obviously stronged the electronic interaction for actively mobilization and weakened the oxidation performance for signally reducing the selective tendency of side reactions to NO. The optimal modification resulted in improving the surface area and enhancing the strong interaction between polyvalent cations in Co/Ni-Mn-SnO to provide more surface adsorbed oxygen, active sites of Mn and Mn, high-content Sn and plentiful Lewis-acidity for more active intermediates, which significantly broadened the activity window of Sn-MnOx, improved the N selectivity by inhibiting NO formation, and also contributed to an acceptable resistances to water and sulfur. At low reaction temperatures, the SCR reactions over three catalysts mainly obeyed the typical Elye-rideal (E-R) routs via the reactions of adsorbed l-NHx (x = 3, 2, 1) and B-NH with the gaseous NO to generate N but also NO by-products. Except for the above basic E-R reactions, as increasing the reaction temperature, the main adsorbed NOx-species were bidentate nitrates that were also active in the Langmuir-Hinshelwood reactions with adsorbed l-NHx species over Co/Ni modified Mn-SnO catalyst.